Q&A – Ask Neil: November 28, 2024
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QUESTION 1
WHAT ARE THE TIMES DURING THE YEAR TO PRUNE KNOCKOUT ROSES?
Question: What are the times of the year when we should be pruning our Knockout roses? Melinda A., Frisco.
Answer: Bush roses are pruned in early February in North Central Texas. That would be just before they start their vigorous spring growth. Your goal will be to remove 50 percent of each plant’s height, pruning the canes just above buds that face out, away from the centers of the plants. However, because of the massive number of canes Knockouts produce, it’s going to be tedious work to cut out each cane one at a time. You may end up using power trimmers for starters, then loppers to trim back the major unwanted canes.
One other warning with Knockouts and Collin County. You are in an epicenter of rose rosette virus currently. Although it is all over the world, it has wrecked roses in Collin County for the past 15 years, none of them more than the Knockouts. I live in Collin County, too, and I’ve been watching them struggle for all that time. Before you go to all this trouble with the pruning be sure that your plants are not infected. Here’s information I’ve left archived on my website.
QUESTION 2
WHAT CAN I DO TO CONTROL GNATS ON MY HOUSEPLANTS?
Question: I’ve been battling gnats in my indoor plants for months. I’ve repotted them all. I’ve used Neem oil spray. I’ve had sticky paper stuck in the pot. I’m not overwatering. The gnats die off for a few weeks, but they always return. No new plants have been brought in. Help! Leslie S., Princeton, Collin County.
Answer: Those are more properly called “fungal gnats,” which gives you an insight into the fact that they are living within fungal (actually algal) growths on the pots, potting soil, or plant stems (or other garden surfaces). Algae grow where there has been an overabundance of moisture at some time in the past. Think of the green mossy growth on clay flowerpots or greenhouse floors that are consistently wet. It’s in that kind of growth that you’ll find the fungal gnats.
These are difficult pests to eliminate because they’re prolific and they’re always in one phase of their life cycle or another. Control begins with letting your plants get just a little bit drier on the tops of their soils before you water. Either you increase the intervals between irrigations (preferable) or you put less water on at a time. Take mature plants out of their pots and repot them into clean, new pots. If you want to reuse the pots you’ve had, soak them for a couple of hours in a tub filled with laundry bleach diluted by 90 percent. Let them sit in the bleach solution for several hours before you rinse them in fresh water. Use a fork to “comb” off the top 1/4-inch of topsoil from their root balls then repot them using fresh potting soil that is free of the pests. All those practices taken together should make major strides in ridding the problem.
QUESTION 3
HOW CAN I DISCOURAGE A BUCK DEER FROM RUBBING THE TRUNK OF A YOUNG OAK?
Question: I can’t catch a break with my new live oaks. A buck deer has rubbed his velvet on one new tree. I sprayed the wound with pruning paint. Is there anything else I should do? Bobby L., Bryan.
Answer: Prevention is the key. You need to keep the buck away from the trunk in the first place. Put a substantial cage around the trunk with wire standing 8 or 10 inches away from the trunk. Leave it in place for several years until the tree is large enough to stand on its own or until the deer becomes disillusioned with your neighborhood entirely.
QUESTION 4
HOW CAN I GET RID OF TREE SHOOTS IN THE SOD?
Question: How can I get rid of tree shoots coming up in my sod? Lance Q., Ponder.
Answer: Where do I start? I zoomed in best I could. Those look like live oak sprouts. You must have a live oak tree somewhere really close. Or, there must have been one in the center of all those sprouts. I can’t see any evidence of one currently near where you were standing when you took the photo.
Here I go:
• Dig 2 or 3 of the sprouts carefully to see if they are tethered to a larger root. If so, they are root sprouts and not seedlings.
• If they are seedlings (not tethered to a larger root), simply mowing will discourage them quickly.
• If they are root sprouts from a tree that no longer exists, then you can apply a broadleafed weedkiller spray (containing 2,4-D) to eliminate them over a several-month period during the growing season.
• If they are root sprouts from a living tree you will have to remove them physically. Any herbicide would risk damaging the mother tree. Use a sharpshooter spade to slice through them several inches below ground level. It’s easiest when the ground is wet. It sounds very tedious, but it shouldn’t take more than a few times across the yard over 12 to 18 months.
QUESTION 5
WHAT IS ALL OVER MY MEXICAN PETUNIAS I PLANTED THIS YEAR?
Question: I planted 12 Mexican petunias (ruellias) this year, late summer. All bloomed well and appeared to be growing well, although three developed this issue with an insect, disease, or whatever. Thoughts? Buddy W., Georgetown.
Answer: I can’t tell for sure. I think I had a similar question several years back here. Perhaps someone will refresh my memory. Please send that note to gretchen@sperrygardens.com, not to the Q&A mailbox. In the meantime, the Web searching I’ve done seems to suggest this is probably mealybugs. They’re a common insect pest of coleus and several other outdoor and indoor plants. I’ll let you do some Googling to see if that might be a match. On a plant that is not a food crop like Mexican petunias, a systemic insecticide would not be a problem. The plants will die to the ground over the winter. Remove and destroy all the stem and leaf stubble. Hopefully you’ll get a fresh start come spring.
(I’ll let you know here in future weeks if I hear anything back from our readers.)
QUESTION 6
WHAT WILL KILL WILD ONIONS?
Question: What will kill wild onions? I have sprayed 2,4-D mixed with a surfactant, but it didn’t seem to have any effect. Can you recommend a product that will work? Dustin I., Fort Worth.
Answer: Some of the “Trimec” products (containing 2,4-D in tandem with two other broadleafed herbicides) proudly proclaim on their labels, “Even kills wild onions!” They wouldn’t go out of their ways to make such claims if they weren’t effective. Be sure you have tried one of the combination products and that you used it at the time of year and in the method recommended. Wild onions are indeed difficult because of their comparatively small leaf area to absorb the herbicide, the fact that the leaves are waxy, the fact that the leaves stand mostly vertically allowing for rapid runoff, and that bulbs are involved – they require more herbicide than normal roots. You need to spray while the weed is growing actively, and you should not mow for several days before or after you spray to give the active ingredient time to get into the plant.
Put in simpler terms: I think the problem was more in technique than in finding a replacement product.
QUESTION 7
HOW CAN I STORE MY IRIS BEFORE REPLANTING THEM?
Question: My old iris bed has become full of weeds and vines. I have decided to dig up the whole thing. I’ll try to kill all the invaders. Is there a way to save my iris to replant in the future? If so, how should I store them? Elizabeth S., McLennan
Answer: When you dig and divide iris you need to replant them as soon as you can. You really don’t “store” them since you’re working with roots and not bulbs. I’d suggest replanting them as soon as you can get the garden soil prepared. If necessary, perhaps you should plant them into a new garden bed prepared just for them. Another option would be to plant them into pots so they can start developing new roots over the winter. At a bare minimum, find a place where you can “heel them into loose garden soil” somewhere. If you leave them out in a cardboard box until you get around to planting them, they will shrivel and dry rather quickly.